Pivotal role of mTOR signaling in hepatocellular carcinoma.
OBJECTIVE
The advent of targeted therapies in hepatocellular carcinoma (HCC) has underscored the importance of pathway characterization to identify novel molecular targets for treatment. We evaluated mTOR signaling in human HCC, as well as the antitumoral effect of a dual-level blockade of the mTOR pathway.


METHODS
The mTOR pathway was assessed using integrated data from mutation analysis (direct sequencing), DNA copy number changes (SNP-array), messenger RNA levels (quantitative reverse-transcription polymerase chain reaction and gene expression microarray), and protein activation (immunostaining) in 351 human samples [HCC (n = 314) and nontumoral tissue (n = 37)]. Effects of dual blockade of mTOR signaling using a rapamycin analogue (everolimus) and an epidermal/vascular endothelial growth factor receptor inhibitor (AEE788) were evaluated in liver cancer cell lines and in a xenograft model.


RESULTS
Aberrant mTOR signaling (p-RPS6) was present in half of the cases, associated with insulin-like growth factor pathway activation, epidermal growth factor up-regulation, and PTEN dysregulation. PTEN and PI3KCA-B mutations were rare events. Chromosomal gains in RICTOR (25% of patients) and positive p-RPS6 staining correlated with recurrence. RICTOR-specific siRNA down-regulation reduced tumor cell viability in vitro. Blockage of mTOR signaling with everolimus in vitro and in a xenograft model decelerated tumor growth and increased survival. This effect was enhanced in vivo after epidermal growth factor blockade.


CONCLUSIONS
MTOR signaling has a critical role in the pathogenesis of HCC, with evidence for the role of RICTOR in hepato-oncogenesis. MTOR blockade with everolimus is effective in vivo. These findings establish a rationale for targeting the mTOR pathway in clinical trials in HCC.
Villanueva
Augusto
A
Mount Sinai Liver Cancer Program, Division of Liver Diseases, Department of Medicine, Mount Sinai School of Medicine, New York, New York 10029, USA.
Chiang
Derek Y
DY
Newell
Pippa
P
Peix
Judit
J
Thung
Swan
S
Alsinet
Clara
C
Tovar
Victoria
V
Roayaie
Sasan
S
Minguez
Beatriz
B
Sole
Manel
M
Battiston
Carlo
C
Van Laarhoven
Stijn
S
Fiel
Maria I
MI
Di Feo
Analisa
A
Hoshida
Yujin
Y
Yea
Steven
S
Toffanin
Sara
S
Ramos
Alex
A
Martignetti
John A
JA
Mazzaferro
Vincenzo
V
Bruix
Jordi
J
Waxman
Samuel
S
Schwartz
Myron
M
Meyerson
Matthew
M
Friedman
Scott L
SL
Llovet
Josep M
JM
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000818:Animals; D017209:Apoptosis; D006528:Carcinoma, Hepatocellular / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D045744:Cell Line, Tumor; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D015151:Immunoblotting; D007150:Immunohistochemistry; D020287:In Situ Nick-End Labeling; D008113:Liver Neoplasms / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D008114:Liver Neoplasms, Experimental / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D008297:Male; D051379:Mice; D008819:Mice, Nude; D008875:Middle Aged; D019869:Phosphatidylinositol 3-Kinases; D011494:Protein Kinases / Q000096:biosynthesis / Q000235:genetics*; D012334:RNA, Neoplasm / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000235:genetics; D058570:TOR Serine-Threonine Kinases
D019869:Phosphatidylinositol 3-Kinases; D011494:Protein Kinases; D012334:RNA, Neoplasm; D058570:TOR Serine-Threonine Kinases; C546842:MTOR protein, human; C546843:mTOR protein, mouse